Medfly Quarantine Affects Solano Farms

Taylor HillmanEnvironment, Pest Update

After dodging the pest-quarantine bullet for more than a decade, a Mediterranean fruit fly quarantine has been established in an agricultural area of Solano County.

There have been several Medfly quarantines in California in recent years, but they have been located in urban and suburban areas, mainly in Southern California, with minimal impact on agricultural operations.

That all changed a few days ago, when the Solano County agricultural commissioner, in cooperation with the California Department of Food and Agriculture and the U.S. Department of Agriculture, announced discovery of four adult Medflies in insect traps in a suburban area near Fairfield. The finds triggered the quarantine and an extensive survey in the area, including the placement of additional Medfly traps.

The Solano County Medfly finds came in orange, Asian pear and quince trees. Eradication efforts include the release of hundreds of thousands of sterile male Medflies to breed with fertile females, with the aim of preventing another generation of the pests.

CDFA said it considers the Medfly to be “the most important agricultural pest in the world,” in part because it has one of the widest host ranges of any fruit fly pest.

Medflies can damage more than 250 types of fruits and vegetables, which could cause significant impacts to California agricultural exports and backyard gardens.

Damage occurs when the female fly lays eggs inside the fruit; the eggs then hatch into maggots that tunnel through the flesh of the fruit, making it unfit for consumption.

The last Medfly quarantine in the area occurred 10 years ago in nearby Dixon. As a result of that quarantine, growers in the region suffered more than $1 million in losses when they were unable to ship their commodities out of the immediate area.

The Fairfield quarantine affects growers such as Derrick Lum, who produce crops within the quarantine zone. Lum said he will feel the financial impact this month when his eight acres of persimmons are ready to be harvested, as well as 13 acres of walnuts.

“The Medfly is having a great effect on me and other growers,” Lum said. “We are under a quarantine now, and the state is handling this. They found the first fly at the end of August, and it raised great concerns among growers in the county.”

Recognizing the risk to his crops after the original fly was detected, Lum took a proactive approach, asking the agricultural commissioner what protocol the state would require to permit him to ship his commodities, should discovery of more flies trigger a quarantine.

The answer was to apply an organic insecticide to the crops four times during a 30-day period. Lum decided to do that, with the first application taking place on Sept. 7 and the final one to be applied this week.

“If I had waited, my crops would be lost because I wouldn’t have been allowed to ship any product until I satisfied the CDFA’s protocol,” he said. “Once I complete the fourth spray, I will be golden and I will be allowed to ship across county lines and abroad.”

Lum described the Medfly quarantine requirements as an unforeseen, added expense.

“But this is part of my farm crop and commodities that provide income, and I can’t risk losing it,” he said. “We are spending money already all year long, waiting for the fruit to harvest, and we can’t risk losing the crop. That would be a major profit deficit.”

It’s not known how many other Solano County farmers also face Lum’s predicament. Several crops grown in the area had already been harvested prior to the quarantine, including about half of the winegrapes. The quarantine is expected to last until spring, unless more Medflies are trapped, which would result in extending the quarantine.

First found in California in 1975, the Medfly became a more widespread problem in 1980-81, when infestations in both Northern and Southern California led to a concerted eradication program, which ultimately proved successful.

But repeated small infestations in the Los Angeles Basin prompted CDFA to inaugurate a Mediterranean Fruit Fly Preventive Release Program in 1996. The program conducts ongoing releases of sterile male Medflies in portions of Los Angeles, Orange, Riverside and San Bernardino counties.

The majority of pest finds occur in urban and suburban areas, CDFA said, most commonly when travelers bring fruit and vegetables into the state from infested regions of the world.

The agency encourages people to follow advice given in its “Don’t Pack a Pest” program, which can be found at

Steve Adler is associate editor of Ag Alert. He may be contacted at sadler@cfbf.comPermission for use is granted by the California Farm Bureau Federation.